The present invention broadly relates to motors and actuators of both macroscopic and microscopic scale, and deals more particularly with an actuator and a related method for moving objects using ultrasonic energy.
Miniaturization of motors, actuators and similar machine parts is receiving increasing attention because of the new uses of these devices made possible because of their small size. Additionally, these devices can be manufactured in large quantities at low piece-part cost. Current designs of miniaturized machine parts can be categorized according to size or scale. Macroscopic machine parts have a length in the range of approximately 1 to 10 inches, and while microscopic machine parts, sometimes referred to as MEMS (Micro Electro Mechanical Systems) have a length in the range of 0.01 to 1 inch.
In any event, existing miniaturized actuators and motors of both macroscopic of microscopic size are essentially replicas of larger motors, and thus include such component parts as windings, stators, gears, transmission links, etc. These miniaturized parts must be assembled with high precision in order to produce an operable device providing the desired function, e.g. movement of an electrically activated component that then mechanically engages other parts to induce motion. Depending upon the engagement configuration, this motion may be linear in any of several axes, rotary, circular, etc. Because of the number of complex parts that must be assembled with a high degree of precision, the yields of parts meeting target specifications and performance are relatively low using current manufacturing processes. These low yields in turn increase the cost of the parts. Accordingly, it would be desirable to provide a new form of actuator and related method for inducing movement of an object on a microscopic or macroscopic scale which eliminates the problems mentioned above.
It is therefore an object of the present invention to provide an actuator and related method for inducing motion of an object which utilizes an ultrasonic transducer as the prime motive power source.
Another object of the invention is to provide an actuator and related method of the type mentioned above which employs well known piezoelectric devices powered by an alternating current power supply that generates ultrasonic vibrations which can be applied to the surface of an object in order to induce motion of the object.
A further object of the invention is to provide an actuator and method as generally described above, which is especially simple to manufacture at low cost while providing high manufacturing yields in the production process.
Another object of the invention is to provide simple, miniaturized actuators that can be used in combination with each other to produce a variety of movements and motions of an object.
These, and further objects and advantages of the present invention will be clear or will become apparent during the course of the following description of a preferred embodiment of the present invention.
According to one aspect of the invention, an ultrasonic motion actuator is provided for inducing movement of an object, comprising an ultrasonic transducer having at least two piezoelectric crystals arranged to generate longitudinal vibratory movement in response to the application thereto of alternating current electrical power. The actuator further includes a transducer tip connected with the crystals that may be used to contact the surface of an object in order to transmit the vibratory movement to the object. The frictional engagement of the tip and accompanying vibratory motion imposes a force on the object that induces motion thereof in a direction determined by the inclination angle of the transducer tip. The transducer, including the tip, may be either macroscopic or microscopic in size. Typically, the tip may be fabricated of a metallic material such as stainless steel. The tip may optionally include a coating of compliant material thereon such as a cured polyimide or rubber. Alternatively, the compliant material may be formed on the surface of the object in order to increase surface friction between the object and the transducer tip.
According to another aspect of the invention, a method is provided for moving an object in a desired direction, comprising the steps of providing an ultrasonic transducer having a tip that vibrates along a longitudinal axis when power is applied to the transducer; urging the tip into vibratory contact with a surface on the object; inclining the transducer tip relative to the surface such that the tip axis is aligned with and pointed in the desired direction of movement; and, supplying electrical power to the transducer so as to cause the tip to vibrate. By changing the angle of inclination of the transducer tip, the force component in the desired direction of travel is either increased or decreased, thus increasing or decreasing the speed of movement of the object. The object may be moved in any of three orthogonal axes by employing a pair of the transducers to engage at least two different surfaces on the object.
The actuator of the present invention can be employed to produce tilting movement of a rigid body about a pivot point by employing a first actuator to hold the body against a fulcrum while a second actuator is employed to impart a moment on one end of the body so as to cause the latter to tilt about the pivot point.
The actuator of the present invention can be advantageously employed as a drive for rotating a disk, such as a computer memory disk, about an axis of rotation. The drive includes an ultrasonic transducer for producing longitudinal vibratory movement when energized by alternating current electrical power, and a transducer tip in contact with and inclined relative to the surface of the disk for transmitting a longitudinal vibratory movement to the disk which results in a force being imposed on the disk that causes it to rotate about the axis.